1. Field of the Invention
The present invention generally relates to a field of navigation for guiding a user to a destination, and more particularly to a method, a device and a system which automatically generate route guide map and route guide sentence for obtaining clear route information.
2. Description of the Related Art
Conventionally, starting with a car navigation system, there has been a variety of navigation systems. As representative examples, a map-guiding-type navigation system which uses route information by visual map and a voice-guiding-type navigation system which carries out navigation by route information by voice instead of visual map or by route information by voice in combination with visual map are known.
As map-guiding-type navigation systems, for example, there are a car navigation system and a portable terminal which navigates with a geographic database and a GPS system. In order to realize such a map-guiding-type navigation system, it is necessary that a device of a user includes route information by visual map and superimposes the present position of the user which is detected by a GPS system or the like on the map information. In addition, it is necessary that the device includes all geographic data for a user's necessity and the geographic data should always be kept up-to-date. Thus, for example, a technology in which the geographic data can be obtained from a communications satellite such that the user does not have to worry about the data capacity of the device is proposed in Japanese laid-open patent application No.6-294659 "MAP DISPLAY DEVICE". In addition, a method in which the map information is compressed so as to decrease an amount of data to be transmitted is proposed in Japanese laid-open patent application No.7-160982 "INSTRUCTION MAP TRANSMISSION SYSTEM".
On the other hand, as voice-guiding-type navigation systems (including the type in combination with the route information by visual map), for example, there are a car navigation system which has a voice guidance capability and a telephone guidance system and the like. In order to realizing the above systems, it is necessary to generate a route guide sentence from the present position of the user and from the geographic data.
Thus, for example, a technology in which a right turn or a left turn or the like according to a turning angle of a selected route is instructed is proposed in Japanese laid-open patent application No.7-146998 "DRIVING LOCATION DISPLAYING DEVICE HAVING VOICE GUIDANCE DEVICE", and a technology for navigating by a driving road name and a place name in the moving direction is proposed in Japanese laid-open patent application No.10-105888 "NAVIGATION DEVICE HAVING VOICE GUIDANCE". In addition, a technology for navigating by a distance from a starting point to a destination, the direction, a target and the like is proposed in Japanese laid-open patent application No.5-334373 "TELEPHONE NAVIGATION DEVICE". Further, in Japanese laid-open patent No.9-318381 "ROUTE GUIDANCE DEVICE", a technology is proposed in which route information by voice is performed by setting an intersection as a guiding point beforehand, and, in the technology, a three-dimensional image for route information is displayed by extracting landmarks from public service facilities such as a public office, a hospital and a school which are indicated by map symbols in geographic data, or from a gas station, a convenience store, a bank and the like. Then, acoustic information (for example, music such as a commercial song) which reminds the user of the landmarks is output.
However, according to the conventional map-guiding-type navigation system, the time for transmission of the geographic data is long because the data amount is very large even if it is compressed. Further, it is difficult to use the geographic data effectively by displaying the route information as it is, because the display size and the resolution of a terminal are generally limited for displaying an image clearly.
In addition, according to the conventional voice-guiding-type navigation system, the system generally relies upon the route information by visual map which coexists with the route information by voice. That is, the system can output only such a representation as a moving direction on a road. Hence, it is difficult to generate effective route guide sentence for complementing the route information. Further, it is difficult to grasp such information which is defined by absolute coordinates as a distance, a direction and the like unless the user is adapted to the place. Furthermore, even when a target such as a landmark is displayed, it is difficult to grasp the information if the landmark is specified independently.
As mentioned above, automatic generation of such route guide map and route guide sentence is not realized currently, and the task for the generation may require manpower, and considerable time and experience. Therefore, there are strong demands for labor-saving and automatization for the generation.